In recent years, with increased demand for high-performance plastics, lots of polymers of various novel properties have been developed and come on the market. Liquid crystalline resins having characteristic parallel arrangement of molecular chains and showing optical anisotropy, such as liquid crystalline polyester, have received particular attention, because of their excellent moldability and mechanical properties, and their applications have been expanded to mechanical components and electric and electronic components. In particular, such liquid crystalline resins are favorably used for electric and electronic components requiring the high flowability, such as connectors.
Accompanied with recent size reduction and weight reduction of equipment, there has been increasing demand for mechanical components and electric and electronic components having the less wall thickness and the more complicated shape. Products using environmentally-conscious lead-free solder have become popular in recent years. Lead-free solder requires extremely higher soldering temperature than conventional solder, so that a molded product obtained from the resin composition is subjected to reflow process at high temperature. Molded products obtained from the conventionally known resin compositions have accordingly the potential warpage during the reflow process. The high degree of warpage in the reflow process causes poor soldering.
To reduce the warpage of the molded product during the reflow process, one proposed liquid crystalline polymer composition obtained by blending 1 to 200 parts by weight of talc having the average particle diameter of 5 to 100 μm and the aspect ratio of 3.0 to 5.0 relative to 100 parts by weight of liquid crystalline polymer (e.g., see JP 2008-138181 A). As liquid crystalline polyester composition having excellent heat resistance and impact resistance, one proposed liquid crystalline polyester composition obtained by blending 10 to 150 parts by weight of talc having the average particle diameter of 2.5 to 3.5 μM and 10 to 150 parts by weight of glass fiber having the average fiber diameter of 3 to 9 μm relative to 100 parts by weight of liquid crystalline polyester (e.g., see JP H04-76049 A). Molded products obtained from such proposed resin compositions reduce the warpage before the reflow process but still have insufficient effect on reduction of the warpage during the reflow process and cause a large variation in flowability.
Molded products obtained from the liquid crystalline resin compositions are often used as metal composite molded products and thereby require the high degree of metal adhesion. The low degree of metal adhesion may cause trouble, such as separating the metal part from the molded product during attachment or detachment of the metal composite molded product to, for example, a substrate. By taking into account the foregoing, with an aim to improve the metal adhesion, one proposed liquid crystalline polyester contains aromatic hydroxydicarboxylic acid, aromatic dicarbonates, diol components and specific phosphorus compound in the molecular chain (e.g., see JP 2005-255914 A). To improve the adhesiveness with epoxy resin or silicone resin, one proposed liquid crystalline resin composition contains 70 to 150 parts by weight of scale-like fillers having the number-average particle diameter of not less than 8 μm relative to 100 parts by weight of liquid crystalline resin (e.g., see JP 2007-254716 A). With an aim to improve the thermal deformation temperature and the blister resistance, one proposed liquid crystalline resin composition obtained by blending 5 to 60 percent by weight of talc having the specific surface area of not greater than 5 m2/g and the average particle diameter of not greater than 40 μm to the thermotropic liquid crystalline polymer (e.g., see JP H04-13758 A). Molded products obtained from such polymer compositions still have insufficient effects on reduction of the variation in flowability and reduction of the warpage during the reflow process.
Recent size reduction and refinement of molded products requires satisfaction of the high degrees of warpage reduction, flowability and metal adhesion. The proposed techniques, however, still do not sufficiently satisfy all these requirements. Therefore, it could be helpful to provide a liquid crystalline polyester composition having high flowability, less variation in flowability, that gives a molded product having high metal adhesion and reduced warpage during reflow process.